In modern database systems, file systems are often used in addition to the database tables. File systems—in particular partitions of a file system—typically serve as a repository for application code and application-specific configuration settings. Vendors of such database systems and vendors of applications that run in conjunction with other database components periodically release upgrades in the form of entirely updated partitions of a file system (e.g., a “major release”), or the vendors may periodically release a patch set covering only “one-off” fixes, or patches covering only a portion of the release (e.g., a “partial release patch set”). System administrators may (or may not) observe the vendor's recommendations for applying patches in a timely fashion (e.g., synchronous or nearly synchronous with patch releases), or they may choose to apply patches in a fashion determined by the system administrators, or, the system administrators may defer applying any or all patches. Further, in some cases, system administrators may make changes to the file system in the form of changes to application code and/or changes to application-specific configuration settings that are not precisely in synchronicity with the vendor's patch releases. Still further, in some cases, system administrators may make changes to the file system, which changes are repugnant with respect to the vendor's patch releases. This results in the situation where the file system may or may not be in a “known” state prior to an upgrade. This creates problems as follows:
When it comes time to upgrade (e.g., by upgrading to a major release) use of legacy techniques force the vendors to one of two choices, both of which are at least partially undesirable and/or destructive:                Choice 1: Completely install the factory-fresh updated portions of a file system.                    Desired Aspects: The factory-fresh updated portions of a file system are in a known state, thus leading to a stable configuration.            Undesired Aspects: The system administrators may have made configuration or code changes which would be overwritten or otherwise destroyed by the factory-fresh installation.                        Choice 2: Apply patches on top of the configuration or code changes made by the system administrators:                    Desired Aspects: Changes made by the system administrators can sometimes be retained.            Undesired Aspects: The application of a patch to a file system that is in an unknown state (e.g., from unknown changes on top of an installation) often results in a system of indeterminate stability.                        
The problem is further exacerbated when the file system is deployed in the context of a database system or an application system that is to be upgraded concurrently with the upgrade of the file system. Yet, using techniques disclosed herein, it is possible to achieve desired aspects without incurring undesired aspects. For example, in some cases it is possible to upgrade while preserving the configuration or code changes made by the system administrators (thus retaining the configuration intentions of the system administrators). In some cases, the changes made by the system administrators can be classified as “don't care”, or “default override”, or can be classified as otherwise benign with respect to the stability of the resulting upgraded system, thus enabling an upgrade while preserving the configuration or code changes made by the system administrators.
What's needed to accomplish these improvements are multiple techniques for upgrading a file system that considers cases when the state of the file system to be upgraded is not factory-fresh, yet it can be unequivocally determined to be a sufficiently stable system so as to be deemed a viable candidate for non-destructive patching.
Unfortunately, legacy techniques do not perform steps for analyzing a file system state to determine a confidence score, nor do legacy techniques perform steps for classifying a file system state to determine a sequence of rebuilding operations. Therefore, there is a need for an improved approach.